Day 49: Polymorphism & Abstraction OOPS (Part 6)

📅 Date: Feb 18, 2026

🧠 Mood: Shapeshifter 🦎

🔥 Topic: OOPs Part 6: Polymorphism & Abstraction

🦎 1. Polymorphism (Bahuroopiya)

The word comes from Greek: Poly (Many) + Morph (Forms).

Real Life Example: YOU.
- In College, you act like a Student.
- At Home, you act like a Son.
- In Game, you act like a Player.
Same Person (Object) -> Different Behaviors.

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⚡ A. Compile Time Polymorphism

Also called Static Binding. The compiler knows before running the code which function to call.

1. Function Overloading

Using the Same Function Name but different parameters.

class Maths {
    public:
    
    // Form 1: 2 Integers
    void add(int a, int b) {
        cout << "Sum is: " << a + b << endl;
    }

    // Form 2: 3 Integers (Same Name!)
    void add(int a, int b, int c) {
        cout << "Sum is: " << a + b + c << endl;
    }
};

int main() {
    Maths m;
    m.add(10, 20);      // Compiler calls Form 1
    m.add(10, 20, 30);  // Compiler calls Form 2
    return 0;
}

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🏃 B. Run Time Polymorphism

Also called Dynamic Binding. This happens while the code is running. This is achieved using Method Overriding.

The Magical `virtual` Keyword

If a Parent and Child have the same function, the Child's function "Overrides" the Parent's function.

class Animal {
    public:
    // "virtual" means: "Let the child decide at runtime"
    virtual void speak() {
        cout << "Animal Speaking..." << endl;
    }
};

class Dog : public Animal {
    public:
    void speak() {
        cout << "Woof Woof!" << endl;
    }
};

int main() {
    Animal *p;      // Parent Pointer
    Dog d;          // Child Object
    p = &d;         // Pointer holding address of Child

    p->speak();     
    // If "virtual" was NOT there -> Output: Animal Speaking...
    // Because "virtual" IS there -> Output: Woof Woof!
    
    return 0;
}

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🎭 2. Abstraction (Hiding Complexity)

Real Life Example: When you press the Car Accelerator, the car moves. Do you know exactly how the engine valves open and fuel injects? NO. That complexity is "Abstracted" (Hidden) from you.

🛠️ Abstract Class

A class that exists only to be inherited. You cannot create an object of it. It contains at least one Pure Virtual Function.

// Abstract Class (Blueprint Only)
class Shape {
    public:
    // Pure Virtual Function (Enforcing a Rule)
    virtual void draw() = 0; 
};

class Circle : public Shape {
    public:
    void draw() {
        cout << "Drawing Circle ◯" << endl;
    }
};

int main() {
    // Shape s; // ❌ ERROR! Cannot create object of Abstract Class
    
    Circle c;
    c.draw(); // ✅ Works
    return 0;
}

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🚀 Day 49 Challenge

1. Create an abstract class Payment with a pure virtual function pay().
2. Create two child classes: GPay and CreditCard.
3. Implement pay() differently in both (e.g., "Paying via UPI" vs "Paying via Card").
4. In main(), use a parent pointer to call both.

Next Up: Day 50 - The Grand Finale (Bank Management System Project).